package com.me.study.jdk8.lambda;

import java.util.List;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

/**
 * 演示 Lambda 表达式（oracle 提供）： 用户类
 *
 * @author ME
 * @date   2019/5/29
 */
public class RosterTest {

    public static void main(String... args) {

        List<Person> roster = Person.createRoster();

        for (Person p : roster) {
            p.printPerson();
        }

        // Approach 1: Create Methods that Search for Persons that Match One
        // Characteristic
        System.out.println("Persons older than 20:");

        printPersonsOlderThan(roster, 20);

        System.out.println();

        // Approach 2: Create More Generalized Search Methods
        System.out.println("Persons between the ages of 14 and 30:");

        printPersonsWithinAgeRange(roster, 14, 30);

        System.out.println();

        // Approach 3: Specify Search Criteria Code in a Local Class
        System.out.println("Persons who are eligible for Selective Service:");

        class CheckPersonEligibleForSelectiveService implements CheckPerson {
            public boolean check(Person p) {
                return p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25;
            }
        }
        printPersons(roster, new CheckPersonEligibleForSelectiveService());

        System.out.println();

        // Approach 4: 内部类
        System.out.println("Persons who are eligible for Selective Service " +
            "(anonymous class):");

        printPersons(roster,
            new CheckPerson() {
                public boolean check(Person p) {
                    return p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25;
                }
            }
        );

        System.out.println();

        // Approach 5: Lambda 表达式
        System.out.println("Persons who are eligible for Selective Service " +
            "(lambda expression):");

        printPersons(roster,
            (Person p) -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25
        );

        System.out.println();

        // Approach 6: 使用标准的函数式接口和 Lambda表达式
        System.out.println("Persons who are eligible for Selective Service " +
            "(with Predicate parameter):");

        printPersonsWithPredicate(roster,
            p -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25
        );

        System.out.println();

        // Approach 7: Use Lamba Expressions Throughout Your Application
        System.out.println("Persons who are eligible for Selective Service " +
            "(with Predicate and Consumer parameters):");

        processPersons(roster,
            p -> p.getGender() == Person.Sex.MALE
                && p.getAge() >= 18
                && p.getAge() <= 25,
            p -> p.printPerson()
        );

        System.out.println();

        // Approach 7, second example
        System.out.println("Persons who are eligible for Selective Service " +
            "(with Predicate, Function, and Consumer parameters):");

        processPersonsWithFunction(roster,
            p -> p.getGender() == Person.Sex.MALE
                && p.getAge() >= 18
                && p.getAge() <= 25,
            p -> p.getEmailAddress(),
            email -> System.out.println(email)
        );

        System.out.println();

        // Approach 8: Use Generics More Extensively
        System.out.println("Persons who are eligible for Selective Service " +
            "(generic version):");

        processElements(roster,
            p -> p.getGender() == Person.Sex.MALE
                && p.getAge() >= 18
                && p.getAge() <= 25,
            p -> p.getEmailAddress(),
            email -> System.out.println(email)
        );

        System.out.println();

        // Approach 9: Use Bulk Data Operations That Accept Lambda Expressions
        // as Parameters
        System.out.println("Persons who are eligible for Selective Service " +
            "(with bulk data operations):");

        roster.stream()
            .filter(
                p -> p.getGender() == Person.Sex.MALE
                    && p.getAge() >= 18
                    && p.getAge() <= 25)
            .map(p -> p.getEmailAddress())
            .forEach(email -> System.out.println(email));
    }

    interface CheckPerson {
        boolean check(Person p);
    }

    // Approach 1: Create Methods that Search for Persons that Match One
    // Characteristic

    public static void printPersonsOlderThan(List<Person> roster, int age) {
        for (Person p : roster) {
            if (p.getAge() >= age) {
                p.printPerson();
            }
        }
    }

    // Approach 2: Create More Generalized Search Methods

    public static void printPersonsWithinAgeRange(
        List<Person> roster, int low, int high) {
        for (Person p : roster) {
            if (low <= p.getAge() && p.getAge() < high) {
                p.printPerson();
            }
        }
    }

    // Approach 3: Specify Search Criteria Code in a Local Class
    // Approach 4: Specify Search Criteria Code in an Anonymous Class
    // Approach 5: Specify Search Criteria Code with a Lambda Expression
    public static void printPersons(List<Person> roster, CheckPerson tester) {
        for (Person p : roster) {
            if (tester.check(p)) {
                p.printPerson();
            }
        }
    }

    // Approach 6: Use Standard Functional Interfaces with Lambda Expressions
    public static void printPersonsWithPredicate(List<Person> roster, Predicate<Person> tester) {
        for (Person p : roster) {
            if (tester.test(p)) {
                p.printPerson();
            }
        }
    }

    // Approach 7: Use Lambda Expressions Throughout Your Application
    public static void processPersons(List<Person> roster, Predicate<Person> tester, Consumer<Person> block) {
        for (Person p : roster) {
            if (tester.test(p)) {
                block.accept(p);
            }
        }
    }

    // Approach 7, second example
    public static void processPersonsWithFunction(List<Person> roster, Predicate<Person> tester,
                                    Function<Person, String> mapper, Consumer<String> block) {
        for (Person p : roster) {
            if (tester.test(p)) {
                String data = mapper.apply(p);
                block.accept(data);
            }
        }
    }

    // Approach 8: Use Generics More Extensively
    public static <X, Y> void processElements(Iterable<X> source, Predicate<X> tester,
                                    Function<X, Y> mapper, Consumer<Y> block) {
        for (X p : source) {
            if (tester.test(p)) {
                Y data = mapper.apply(p);
                block.accept(data);
            }
        }
    }
}
